A known type of high speed food slicing machine uses a rotary cutting wheel carrying radially extending circumferentially spaced, tensioned and pitched thin metal blades for slicing food products such as vegetables, meat products, fruits, etc. that are advanced into the cutting plane of the rotating blades by a conveyor or gravity into slices that can be further processed or directly consumed by a consumer.
Exemplary slicing machines of this type are depicted in U.S. Pat. Nos. 2,482,523 granted Sep. 20, 1949; 3,004,572 granted Oct. 17, 1961; and 2,665,723 granted Jan. 12, 1954, all of which are owned in common with the owner of the invention described herein. U.S. Pat. Nos. 2,482,523 and 3,004,572 show rotary slicers wherein the unsliced food product is advanced to one portion of a generally vertically extending cutting plane of the rotary blades by a generally horizontal conveyor belt system that may include single or multiple belt arrangements that feeds the food products towards an area of the cutting plane where the blades are moving generally downwardly relative to the food product so that the cutting action is across the leading side of the food product and downwardly relative to the food product and the conveyor so that the food product is stabilized by the conveyor during the slicing process. In the machine depicted in U.S. Pat. No. 2,665,723, the food product to be sliced is fed gravitationally vertically towards a horizontal cutting plane defined by rotary cutter blades that are somewhat shorter than the cutter blades in the preceding examples and which are mounted on the cutting wheel which lies generally in a horizontal plane.
In machines of this type, relatively thin stainless steel hardened metal blades having a single sharpened leading edge that may be straight or scalloped are mounted so as to extend radially between a hub and a rim of a cutting wheel much like spokes of a bicycle wheel. Also, in the manner of wheel spokes, the blades are placed in uniform tension by clamping the blades at their ends by tension pin fasteners respectively to the hub and rim of the cutting wheel and then pulling the inboard ends of the blades through the inboard fasteners collectively and uniformly towards the center line of the axis of rotation of the cutting wheel. The blades of such machines, moreover, are forwardly pitched or slanted much like a propulsion propeller or impeller, with the pitch varying between the radially inner and outer ends of the blades to compensate for the difference in blade relative linear speed at the radially inner and outer ends of the blades. The rotating pitched blades throw or impel the cut slices in a forward direction extending transversely of the cutting planes of the blades in the same general direction of advancement of the food product towards the blades and also cause advancement or impelling of the unsliced food product into and through the cutting plane much like a propeller thrusting air or liquid through the plane of rotation of the propeller in a direction resulting from the pitch of the blades and the bevel angle of the sharpened blade leading edge.
Food slicers of the type just described produce somewhat uniform slices during high speed, high volume slicing runs and have enjoyed commercial acceptance by food processors (e.g., canners, frozen food processors, snack food producers, etc.) and value-added processors that prepare food slices for direct consumption. However, because of the dynamics of high speed, high volume slicing of food products of variable size and hardness using tensioned and pitched rotating cutting blades on a rotating cutting wheel, control over quality of slice geometry and dimensions poses a challenge to designers of such machines.
Cutting wheels of the type used in food cutting machines described above typically contain an even multiple of blades that are driven at a rotational speed determine experimentally to produce the best cutting performance for given cutting blades and food products to be sliced. The number of blades installed on the wheel can be varied in an even multiples to maintain the wheel in balance and to vary the slice thickness of the food products moving through the cutting plane of the cutting wheel. Obviously, the fewer the number of blades installed on a given cutting wheel designed to advance unsliced portions of food products a given distance per rotation, the thicker the cut slices will be because the food product is advanced a given distance between blade engagements.
Despite rigorous efforts to design cutting machines of this kind to exacting standards, achieving uniformity of slice thickness and avoidance of slice thickness variation, usually exhibited as a slice having a thicker end or region and a thinner end or region has proven difficult to achieve, particularly in cutting machines using longer, narrower and more flexible blades as exemplified in the above-mentioned U.S. Pat. Nos. 2,482,523 and 3,004,572.
Shorter blades used in a gravity fed machine exemplified in the above-mentioned U.S. Pat. No. 2,665,723 tend to produce relatively uniform dimensioned slices because of the shorter and wider blading that can be used in such machines. The shorter blading reduces flexure of the blades during slicing of the food products so that relatively uniformly dimensioned slices can be produced using such gravity fed machines. However, not all food products can be gravity fed to the cutting blade of a gravity type food cutter on a production scale. Certain food products optimally are fed to the cutting wheel in a generally horizontal direction with the wheel oriented in a generally vertical orientation for a number of reasons known to those in the food cutting field and which are explained in U.S. Pat. No. 2,482,523. Accordingly, cutting uniform slices in high volume using vertically oriented cutting wheels of the type described above and using feed devices for advancing food products to the cutting wheel while using relatively longer blading in the cutting wheel is a recognized goal to be achieved in the field of food product slicing.
In pursuit of this goal, various approaches to solving slice size variation were attempted. These approaches included varying blade shapes and blade mounting systems (location of tension fasteners, etc.). Cutting blade flexure, particularly transverse flexure about a longitudinal axis along the blade length, was identified as a cause of slice irregularities and it was also discovered that a gate action controlling or limiting incremental advancement of the unsliced food product through the cutting plane between slices tended to produce more uniform slices. However, consistent optimum slice uniformity was still not obtained. The use of wide blades to obtain the gating effect secured some improvement and the use of a maximum practical number of wide blades on the cutting wheel enabled the production of thin slices of food products that approached uniformity, but which nonetheless were sufficiently irregular so as to be observable to a casual viewer, particularly when the slices were stacked one on top of the other.
Actually, minor slice thickness irregularity on the order of several thousandth of an inch (or the metric equivalent thereof) which is not observable to the naked eye in any individual slice becomes very observable when the slices are stacked one on top of the other. Such irregularities are not desired by food processors because irregular slices are not attractive when stacked, do not cook or fry uniformly, are not of uniform weight and thickness and tend to complicate the processing procedures, particularly when the processing involves cooking or frying very thin slices of vegetables such as potatoes to be fried for making potato chips. Obviously, sliced products that are to be purchased by consumers that may view the slices in stacked condition should be uniform in thickness for maximum visual appeal and consistent packing, as well.
In accordance with prior art attempts to obtain uniform thickness thinly sliced food products, cutter blades having relatively wider widths were used, with the blades shaped to have longer trailing edges as compared with the leading edges that included a sharpened portion. The wider width blades produced a desired gating or gauging action when sufficient blades were provided on the wheel, which usually operates at a design speed or several discrete design speeds, but blade flexing resulting from contact between the individual blades and the food products still constituted an impediment to achieving uniform slice thicknesses, particularly with harder or fibrous food product that have the ability to deflect or twist the cutting blades.
It was suspected that the speed at which the food product approaches the cutting plane of the cutting wheel could have an influence on the stability of the unsliced food product portion moving through the cutting blades, particularly when the advancement of the unsliced portion was effectively gated or periodically interrupted slightly between the conveyor feed device and the cutting wheel.
U.S. Pat. No. 2,482,523 discusses a relationship between the feeding speed of food products advanced to a vertical cutting wheel containing tensionsed pitched blades but the objective of the system described in the patent is to avoid a gating effect between blades by advancing the food product to the cutting plane of the cutting blades such that the trailing edge of each blade and all portions of the body of the blade between the cutting and trailing edges will be moved out of registry with every section of the food product being cut by the time that section moves axially through the cutting plane over a distance that would carry such section against the cutting blade body. As explained in the patent, in accordance with such design, the cutting blades offered no resistance to the path followed by the food products whereby the food products passed through the cutting plane substantially the same as if they were entire bodies instead of slices. Thus, in accordance with the patent, no part of the broad flat rear faces of the cutting blades abutted against the unsliced portion of the food product advancing through the cutting plane.
In a food cutting machine of the type described herein, wherein it is desired to gauge each slice by advancing the uncut portion of the food product forwardly just enough to precisely locate the unsliced portion in a precise position to be engaged by the next succeeding cutting blade, uniformity of sliced thicknesses prove to be less than desirable.
Accordingly, an objective of the invention is to slice uniform dimensioned slices of food products advanced through a generally vertically oriented cutting wheel of the type described above, particularly thin slices on the order of 0.125" (0.318 cm).